I think two extra personal days is the better choice for the company. Many employees will like it more than the transit pass.
Not every people use the bus or the train. Some employees drive car to work or they live near and walk. For them the transit pass is no useful. But everybody need personal days. For example, last month I had to go to doctor appointment with my mother and I had to use my vacation day for it. If we have personal days, we don't need to use vacation for this kind of things.
Also, personal days are good for rest. Sometimes people feel very tired because of the work and they need one day to relax. When employees are rested, they work more better and they are more happy in the company.
The transit pass is a good idea too, because it can save money for some workers. But I think personal days help all employees, not only some. That's why I choose personal days.